Diffuse Ionized Gas in the Dwarf Irregular Galaxy DDO 53

The spectral characteristics throughout the dwarf irregular galaxy DDO 53 are studied. The results are very similar to those for other irregular galaxies: high excitation and low values of the [SII]/Halpha ratio. The most likely ionization source is photon leakage from the classical HII regions, without any other source, although the interstellar medium of the galaxy is quite perturbed. Moreover, the physical conditions throughout the galaxy do not change very much because both the photon leakage percentage and the ionization temperature are very similar. In addition, the determined metal content for two HII regions indicates that DDO 53 is a low-metallicity galaxy.Comment: 32 pages, 9 figures, 7 tables. AJ, in pres

Physical Conditions in the Dwarf Local Group Irregular Galaxy IC10. I- Diffuse Ionized Gas

A detailed analysis on the physical conditions of the Interstellar Medium in the main body of the Local Group dwarf irregular galaxy IC 10 is carried out using long-slit spectroscopy. Maps of the excitation, the H$\alpha$ flux, [NII]/H$\alpha$ and [SII]/H$\alpha$ are presented. The Diffuse Ionized Gas inside the galaxy is studied. We found that the spectral characteristics are not similar to those for spiral galaxies: the values of the ratios [NII]/H$\alpha$ and [SII]/H$\alpha$ are not as large as in spiral galaxies but the excitation is much larger. These values, especially the large excitation, can be explained by proposing an extra source of ionization. Different sources are studied but any of the models at hand could be really fitted except a combination of photons leaking from the HII regions in addition to the ionization provided by the WR stars present in this galaxy. Shocks are not needed for explaining the line intensity ratios except in a small part in the west side of the galaxy.Comment: 12 pages, 12 figures, accepted for publication in A&

Understanding the influence of filler type and asphalt binder content on the moisture and fatigue resistance of asphalt mortars

An adequate moisture resistance is a key element to guarantee the durability of asphalt materials. This paper identifies the influence of filler typology and bitumen content on the mechanical response of asphalt mortars before and after water action. Two fillers were evaluated: Portland cement and Calcium carbonate, along with different contents of a penetration bitumen (B35/50). Stiffness, ductility, and fatigue were evaluated through a new protocol for asphalt mortar samples using a 3-point-bending test on DMA (Dynamic Mechanical Analyzer). The use of Portland cement presents higher stiffness, lower ductility, and improved fatigue and water resistance compared to Calcium carbonate. It is also possible to optimize bitumen content based on fatigue results. Content beyond the optimal reduce variations after water action but compromise fatigue resistance. Lower content leads to a poorer performance in both terms. This methodology enables asphalt mortar characterisation as a tool to optimise the design of asphalt materials.La influencia del tipo de polvo mineral y contenido de ligante bituminoso en la resistencia a la humedad y fatiga de morteros bituminosos. La resistencia al agua es clave para garantizar la durabilidad de los materiales asfálticos. Este estudio identifica la influencia del polvo mineral y contenido de betún en la respuesta mecánica de morteros bituminosos antes y después de la humedad. Se evaluaron dos tipos de filler: cemento Portland y carbonato cálcico (filler calizo), junto con distintos contenidos de betún (B35/50). Rigidez, ductilidad y fatiga fueron evaluados mediante un nuevo ensayo de fatiga a tres puntos para morteros empleando DMA (Dynamic Mechanical Analyzer). El cemento presenta más rigidez, menos ductilidad y mayor resistencia al agua y fatiga que el filler calizo. Los resultados de fatiga permiten además optimizar el contenido de betún. Contenidos por encima del óptimo reducen variaciones tras la humedad pero comprometen la resistencia a fatiga. Contenidos menores conllevan un peor comportamiento en ambos términos. Esta metodología permite usar la caracterización de morteros bituminosos para optimizar el diseño de materiales asfálticos

Metallicity determination in gas-rich galaxies with semiempirical methods

A study of the precision of the semiempirical methods used in the determination of the chemical abundances in gas-rich galaxies is carried out. In order to do this the oxygen abundances of a total of 438 galaxies were determined using the electronic temperature, the $R_{23}$ and the P methods. The new calibration of the P method gives the smaller dispersion for the low and high metallicity regions, while the best numbers in the turnaround region are given by the $R_{23}$ method. We also found that the dispersion correlates with the metallicity. Finally, it can be said that all the semiempirical methods studied here are quite insensitive to metallicity with a value of $8.0\pm0.2$ dex for more than 50% of the total sample. \keywords{ISM: abundances; (ISM): H {\sc ii} regions}Comment: 26 pages, 9 figures and 2 tables. To appear at AJ, January 200

The warm ionized medium in spiral galaxies

This article reviews observations and models of the diffuse ionized gas that permeates the disk and halo of our Galaxy and others. It was inspired by a series of invited talks presented during an afternoon scientific session of the 65th birthday celebration for Professor Carl Heiles held at Arecibo Observatory in August 2004. This review is in recognition of Carl's long standing interest in and advocacy for studies of the ionized as well as the neutral components of the interstellar medium.Comment: 29 pages, 19 figures; accepted by Reviews of Modern Physic

Evaluation of appendicitis risk prediction models in adults with suspected appendicitis

Background Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis. Methods A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis). Results Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent). Conclusion Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified

The chemical content of a sample of dwarf irregular galaxies

We present abundances of neon, nitrogen and oxygen of some nearby dwarf irregular galaxies. The elemental abundances are retrieved from long-slit spectroscopy of H i