Kinematic study of planetary nebulae in NGC 6822

By measuring precise radial velocities of planetary nebulae (which belong to the intermediate age population), H II regions, and A-type supergiant stars (which are members of the young population) in NGC 6822, we aim to determine if both types of population share the kinematics of the disk of H I found in this galaxy. Spectroscopic data for four planetary nebulae were obtained with the high spectral resolution spectrograph Magellan Inamori Kyocera Echelle (MIKE) on the Magellan telescope at Las Campanas Observatory. Data for other three PNe and one H II region were obtained from the SPM Catalog of Extragalactic Planetary Nebulae which employed the Manchester Echelle Spectrometer attached to the 2.1m telescope at the Observatorio Astron\'omico Nacional, M\'exico. In the wavelength calibrated spectra, the heliocentric radial velocities were measured with a precision better than 5-6 km s$^{-1}$. Data for three additional H II regions and a couple of A-type supergiant stars were collected from the literature. The heliocentric radial velocities of the different objects were compared to the velocities of the H i disk at the same position. From the analysis of radial velocities it is found that H II regions and A-type supergiants do share the kinematics of the H I disk at the same position, as expected for these young objects. On the contrary, planetary nebula velocities differ significantly from that of the H I at the same position. The kinematics of planetary nebulae is independent from the young population kinematics and it is closer to the behavior shown by carbon stars, which are intermediate-age members of the stellar spheroid existing in this galaxy. Our results are confirming that there are at least two very different kinematical systems in NGC 6822

Optical properties of polycrystalline Cd(1-x)Mn(x)Te

Bulk polycrystalline cadmium manganese telluride, Cd(l-x)Mn(x)Te, was manufactured in several compositions by a synthesis process. The structure of the obtained compounds was the characteristic zinc-blende polycrystalline pattern being the grain size lOOj=20 nm. These materials are manufactured to replace single-crystal compounds in some magneto-optical devices. The cut-off wavelength and the Verdet constant are the same as the single-crystals with identical composition. A polarized laser beam, after having passed through a sample of 0.76 mm thickness, was depolarized less than 2.5%, and 90% of its energy was spread into a 2º cone. Scattering of light is produced because of the polycrystalline structure of these ompounds. Some scattering diagrams, due to the diffraction and Mie scattering in the polycrystalline grains are shown

Solar photocatalytic degradation of polyethylene terephthalate nanoplastics: Evaluation of the applicability of the TiO2/MIL-100(Fe) composite material

For the first time, TiO2/MIL-100(Fe) photocatalysts supported on perlite mineral particles prepared by the solvothermal/microwave methods and post-annealing technique were tested in the degradation of polyethylene terephthalate nanoplastics (PET NPs). Powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy, N2 physisorption, photoluminescence emission spectroscopy, photocurrent response, and electrochemical impedance spectroscopy were used to characterize the as-prepared materials. The response surface methodology approach was used to study the effects: pH of the NPs suspension and incorporated amount of MIL-100(Fe) on the TiO2/MIL-100(Fe) catalyst to optimize the photocatalytic degradation of the PET NPs under simulated solar light. The degradation of the PET NPs was evaluated by measuring turbidity and carbonyl index (FTIR) changes. The total organic carbon (TOC) in the solution during the degradation of the PET NPs was assessed to measure NPs oxidation into water-soluble degradation by-products. The active species involved in the photocatalytic degradation of PET NPs by the TiO2/MIL-100(Fe) composite was further examined based on trapping experiments. The use of 12.5 wt% TiO2/MIL-100(Fe) catalyst showed improved photocatalytic efficacy in the oxidation of PET NPs at pH 3 under simulated sunlight compared to bare TiO2. The increase in the carbonyl index (CI = 0.99), the reduction in the turbidity ratio (0.454), and the increase in the content of TOC released (3.00 mg/L) were possible with 12.5 wt% TiO2/MIL-100(Fe) material. In contrast, the PET NPs were slowly degraded by TiO2-based photocatalysis (CI = 0.96, turbidity ratio = 0.539, released TOC = 2.12 mg/L). The mesoporous TiO2/MIL-100(Fe) composites with high specific surface area, capacity to absorb visible light, and effective separation of photogenerated electron-hole charges clearly demonstrated the enhancement of the photocatalytic performance in the PET NPs degradation under simulated solar light

Optical spectroscopic study of the growth dynamics of radio-frequency-sputtered YBa2Cu3O(7-x) thin films

An optical spectroscopic study of the plasma produced during rf sputtering of an YBa2Cu3O7-x target was performed to analyze two basic properties of the deposition process: resputtering effects and oxidation mechanisms. Strong emissions of all the species above a value of the target voltage were found. These observations are associated to a strong secondary electron emission of the target which originates a negative self-bias of the substrate and a subsequent resputtering by argon cations. The addition of different amounts of oxygen to the discharge reveals that preoxidation in the gas phase may decrease the oxygen content in the films: the oxidation of the films is dominated by atomic oxygen

Chemical behavior of the Dwarf Irregular Galaxy NGC 6822. Its PN and HII region abundances

We aim to derive the chemical behavior of a significant sample of PNe and HII regions in the irregular galaxy NGC 6822 The selected objects are distributed in different zones of the galaxy. Due to the faintness of PNe and HII regions in NGC 6822, to gather spectroscopic data with large telescopes is necessary. We obtained a well suited sample of spectra by employing VLT-FORS 2 and Gemini-GMOS spectrographs. Ionic and total abundances are calculated for the objects where electron temperatures can be determined through the detection of [OIII] \lambda 4363 or/and [NII] \lambda 5755 lines. A "simple" chemical evolution model has been developed and the observed data are used to compute a model for NGC 6822 in order to infer a preliminary chemical history in this galaxy. Confident determinations of He, O, N, Ne, S and Ar abundances were derived for a sample of 11 PNe and one HII region. We confirm that the present ISM is chemically homogeneous, at least in the central 2 kpc of the galaxy, showing a value 12+log O/H = 8.06$\pm$0.04. From the abundance pattern of PNe, we identified two populations: a group of young PNe with abundances similar to HII regions and a group of older objects with abundances a factor of two lower. A couple of extreme Type I PNe were found. No third dredge-up O enrichement was detected in PNe of this galaxy. The abundance determinations allow us to discuss the chemical behavior of the present and past ISM in NGC 6822. Our preliminary chemical evolution model predicts that an important gas-mass lost occurred during the first 5.3 Gyr, that no star higher than 40 M$_\odot$ was formed, and that 1% of all 3-15 M$_\odot$ stars became binary systems progenitors to SNIa.Comment: 15 pages, 3 figures and 4 tables. A&A, Accepted 13/06/200

Seguridad IoT: Principales amenazas en una taxonomía de activos

El Internet de las Cosas (IoT) es una extensión de internet al integrar redes móviles, internet, redes sociales y cosas inteligentes para proporcionar mejores servicios o aplicaciones a los usuarios, uno de los mayores retos que tiene IoT son los problemas de seguridad relacionados con las amenazas, ataques, vulnerabilidades, etc. En este artículo, se proporciona una taxonomía de sus activos mediante la agrupación de los diferentes elementos que conforman un ecosistema IoT, para determinar qué elementos podrían estar afectados en la adquisición, el intercambio y el procesamiento de información ante las posibles amenazas existentes. La metodología utilizada consta de cuatro pasos, comenzando con la definición del alcance y juicios de expertos en el área de IoT, la investigación de escritorio, el análisis y desarrollo, redacción y validación del informe, llegando a obtener una clasificación y análisis de las principales amenazas según la categorización de los diferentes tipos de amenazas existentes y el nivel de impacto de riesgo que estas generan identificando qué amenazas pueden mitigarse y el riesgo que puedan tener en cada entorno IoT. Como resultado se aporta con una taxonomía de seguridad que podrá ser usada para evaluar el nivel de impacto de riesgo de toda una arquitectura IoT

Digestabilidad, energía digestible y metabolizable del sacha inchi (Plukenetia volubilis L) peletizado y extruido en cuyes (Cavia porcellus)

El estudio tuvo como objetivo evaluar la digestibilidad de los nutrientes y energía digestible y metabolizable de la semilla y torta de sacha inchi (Plukenetia volubilis L) precocida y procesada (peletizado y extruido) en cuyes. En cada ensayo se utilizaron 15 cuyes machos, de 3 meses edad y peso promedio de 700 g. El peletizado se realizó a 87 °C y la extrusión a 105 °C. La digestibilidad y metabolicidad fue determinada utilizando el método de sustitución y colección total de excretas (heces y orina). Los valores de digestibilidad aparente (%) para materia seca, proteína bruta, fibra cruda y extracto etéreo para la semilla peletizada fueron de 54.4, 79.6, 27.0, 76.1 y semilla extruida de 48.7, 83.5, 16.2 y 81.7 respectivamente; mientras que para torta peletizada fueron de 82.5, 81.2, 98.7, 65.9 y torta extruida 76.7, 83.2, 92.8 y 62.4. La energía digestible en la semilla peletizada y extruida fue de 3296 y 3681 kcal/kg de materia seca, y en la torta peletizada y extruida fue de 4621 y 4161 kcal/kg de materia seca, respectivamente. La energía metabolizable en la semilla peletizada y extruida fue de 2676 y 3243 kcal/kg de materia seca, y en la torta peletizada y extruida fue de 4346 y 4137 kcal/kg de materia seca, respectivamente. El tipo de procesamiento no afectó los valores energéticos en la semilla y torta de sacha inchi