Density waves and star formation in grand design spirals

HII regions in the arms of spiral galaxies are indicators of recent star-forming processes. They may have been caused by the passage of the density wave or simply created by other means near the arms. The study of these regions may give us clues to clarifying the controversy over the existence of a triggering scenario, as proposed in the density wave theory. Using H$\alpha$ direct imaging, we characterize the HII regions from a sample of three grand design galaxies: NGC5457, NGC628 and NGC6946. Broad band images in R and I were used to determine the position of the arms. The HII regions found to be associated with arms were selected for the study. The age and the star formation rate of these HII regions was obtained using measures on the H$\alpha$ line. The distance between the current position of the selected HII regions and the position they would have if they had been created in the centre of the arm is calculated. A parameter, T, which measures whether a region was created in the arm or in the disc, is defined. With the help of the T parameter we determine that the majority of regions were formed some time after the passage of the density wave, with the regions located `behind the arm' (in the direction of the rotation of the galaxy) the zone they should have occupied had they been formed in the centre of the arm. The presence of the large number of regions created after the passage of the arm may be explained by the effect of the density wave, which helps to create the star-forming regions after its passage. There is clear evidence of triggering for NGC5457 and a co-rotation radius is proposed. A more modest triggering seems to exist for NGC628 and non significant evidence of triggering are found for NGC6946.Comment: 10 pages, 20 figures, accepted for publication in A&

Human myiasis in Ecuador.

We review epidemiological and clinical data on human myiasis from Ecuador, based on data from the Ministry of Public Health (MPH) and a review of the available literature for clinical cases. The larvae of four flies, Dermatobia hominis, Cochliomyia hominivorax, Sarcophaga haemorrhoidalis, and Lucilia eximia, were identified as the causative agents in 39 reported clinical cases. The obligate D. hominis, causing furuncular lesions, caused 17 (43.5%) cases distributed along the tropical Pacific coast and the Amazon regions. The facultative C. hominivorax was identified in 15 (38%) clinical cases, infesting wound and cavitary lesions including orbital, nasal, aural and vaginal, and occurred in both subtropical and Andean regions. C. hominivorax was also identified in a nosocomial hospital-acquired wound. Single infestations were reported for S. haemorrhoidalis and L. eximia. Of the 39 clinical cases, 8 (21%) occurred in tourists. Ivermectin, when it became available, was used to treat furuncular, wound, and cavitary lesions successfully. MPH data for 2013–2015 registered 2,187 cases of which 54% were reported in men; 46% occurred in the tropical Pacific coast, 30% in the temperate Andes, 24% in the tropical Amazon, and 0.2% in the Galapagos Islands. The highest annual incidence was reported in the Amazon (23 cases/100,000 population), followed by Coast (5.1/100,000) and Andes (4.7/100,000). Human myiasis is a neglected and understudied ectoparasitic infestation, being endemic in both temperate and tropical regions of Ecuador. Improved education and awareness among populations living in, visitors to, and health personnel working in high-risk regions, is required for improved epidemiological surveillance, prevention, and correct diagnosis and treatment

Distributed Computing in the Asynchronous LOCAL model

The LOCAL model is among the main models for studying locality in the framework of distributed network computing. This model is however subject to pertinent criticisms, including the facts that all nodes wake up simultaneously, perform in lock steps, and are failure-free. We show that relaxing these hypotheses to some extent does not hurt local computing. In particular, we show that, for any construction task $T$ associated to a locally checkable labeling (LCL), if $T$ is solvable in $t$ rounds in the LOCAL model, then $T$ remains solvable in $O(t)$ rounds in the asynchronous LOCAL model. This improves the result by Casta\~neda et al. [SSS 2016], which was restricted to 3-coloring the rings. More generally, the main contribution of this paper is to show that, perhaps surprisingly, asynchrony and failures in the computations do not restrict the power of the LOCAL model, as long as the communications remain synchronous and failure-free

Geodesic Deviation Equation in Bianchi Cosmologies

We present the Geodesic Deviation Equation (GDE) for the Friedmann-Robertson-Walker(FRW) universe and we compare it with the equation for Bianchi type I model. We justify consider this cosmological model due to the recent importance the Bianchi Models have as alternative models in cosmology. The main property of these models, solutions of Einstein Field Equations (EFE) is that they are homogeneous as the FRW model but they are not isotropic. We can see this because they have a non-null Weyl tensor in the GDE.Comment: Submitted to Journal of Physics: Conference Series (JPCS), ERE200

Path Integral Approach to Strongly Nonlinear Composite

We study strongly nonlinear disordered media using a functional method. We solve exactly the problem of a nonlinear impurity in a linear host and we obtain a Bruggeman-like formula for the effective nonlinear susceptibility. This formula reduces to the usual Bruggeman effective medium approximation in the linear case and has the following features: (i) It reproduces the weak contrast expansion to the second order and (ii) the effective medium exponent near the percolation threshold are $s=1$, $t=1+\kappa$, where $\kappa$ is the nonlinearity exponent. Finally, we give analytical expressions for previously numerically calculated quantities.Comment: 4 pages, 1 figure, to appear in Phys. Rev.

Formulación de una estrategia didáctica para la enseñanza del cálculo diferencial

El presente trabajo tiene como objetivo proponer una estrategia didáctica que promueva el aprendizaje de la derivada a partir del estudio de los conocimientos previos que poseen los estudiantes de primer semestre de ingeniería de la Universidad Católica de Colombia sobre el concepto de la derivada. Se planteó dentro del enfoque cualitativo interpretativo, estudiando una realidad educativa, con un diseño metodológico descriptivo interpretativo, de alcance exploratorio y descriptivo que permite cumplir el objetivo de investigación. Presenta los conocimientos previos a fin de interpretarlos y diseñar la estrategia didáctica. Los resultados muestran que, para el cálculo del límite, el enfoque es netamente algorítmico. Además, a pesar de que existe claridad en torno a los conceptos de pendiente y de función lineal, esta no existe cuando se trata de la interpretación geométrica de la gráfica de otro tipo de funciones. Adicional a lo anterior, se evidenciaron grandes deficiencias de tipo operacional en la parte aritmética y de productos notables y factorización de polinomios así como identificación de variables y su relación entre ellas. Con base en los resultados, se diseñó una estrategia didáctica, con un análisis y secuenciación de contenidos, recursos pedagógicos y actividades que van desde una fase exploratoria, de refuerzo y activación, de significación, aplicación y generación de conocimiento, hasta una actividad de transferencia de conocimiento.Abstract: Job that aims to develop a teaching strategythat promotes meaningful learning from the study of previous knowledge that students in the second semester of engineering at Catholic University of Colombia have on the concept of the derivative. It arises in the interpretative qualitative approach, studying an educational reality, with an interpretive descriptive methodological design, an explorer and descriptive scope that allows fulfilling the objective of the research. Describes the knowledge background to interpret and design the teaching strategy. The results show that for the calculation of the limit, the focus is purely algorithmic. Also, that the concept of slope and linear function is clear, it does not exist when it comes to the geometric interpretation of the graph of other functions. In addition to the above major operational deficiency type in the arithmetic part and remarkable products and factoring polynomials and identification of variables and the relationship between them are found. Based on the results, a teaching strategy is designed with an analysis and sequencing of the contents, didactic resources and activities from exploration, reinforcement and activation, with significance, application and generation of knowledge, to a knowledge transfer activity

Glacial-interglacial vegetation dynamics in South Eastern Africa coupled to sea surface temperature variations in the Western Indian Ocean

Glacial-interglacial fluctuations in the vegetation of South Africa might elucidate the climate system at the edge of the tropics between the Indian and Atlantic Oceans. However, vegetation records covering a full glacial cycle have only been published from the eastern South Atlantic. We present a pollen record of the marine core MD96-2048 retrieved by the Marion Dufresne from the Indian Ocean similar to 120 km south of the Limpopo River mouth. The sedimentation at the site is slow and continuous. The upper 6 m (spanning the past 342 Ka) have been analysed for pollen and spores at millennial resolution. The terrestrial pollen assemblages indicate that during interglacials, the vegetation of eastern South Africa and southern Mozambique largely consisted of evergreen and deciduous forests. During glacials open mountainous scrubland dominated. Montane forest with Podocarpus extended during humid periods was favoured by strong local insolation. Correlation with the sea surface temperature record of the same core indicates that the extension of mountainous scrubland primarily depends on sea surface temperatures of the Agulhas Current. Our record corroborates terrestrial evidence of the extension of open mountainous scrubland (including fynbos-like species of the high-altitude Grassland biome) for the last glacial as well as for other glacial periods of the past 300 Ka

Investigation of optical and physico-chemical properties of titanium-doped V2O5 nanofilms

In this paper, undoped and Ti-doped V2O5 thin films were fabricated and deposited onto glass substrates using a > method. Then, the effects of Ti-doping on the optical properties of the thin films were investigated. Titanium doping concentration of 0.25-0.75 at.% has been investigated. After treatment in air at different temperatures, the obtained films was characterised by various techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL). It was found that the as-obtained doped films possessed thermochromic properties and optical switching characters. According to optical tests, thin linings of vanadium dioxide alloyed with Ti have optical properties that are effective for application. Because of their capacity to automatically control interior solar irradiation, lower air-conditioning energy consumption, and maintain a comfortable internal thermal climate, smart windows have drawn increased interest in recent years. The doping strategy and integrating with functional coatings can regulate the properties of obtained V2O5 films.6 página