Spontaneous posterior wall external canal cholesteatoma.

A 44-year-old woman with a history negative for trauma, inflammation, surgery, or radiotherapy of the head or neck was referred for cerumen removal. Following the cerumen removal, a dehiscence of the posterior wall of the bony canal with squamous debris suggestive of external canal cholesteatoma was ob-served (figure).This is a rare condition usually involving the inferior auditory canal

Cathodic protection with localised galvanic anodes in slender carbonated concrete elements

A combined experimental and numerical investigation was carried out with the aim of determining whether few localised galvanic anodes per unit length could protect the reinforcement of slender carbonated concrete elements, exposed to atmospheric conditions, which could not be repaired with traditional methods. Initially, the cathodic behaviour of steel under galvanostatic polarisation was determined on small-size specimens obtained from a real element. A correlation of potential versus applied current was obtained. The current distribution in slender elements was then determined through finite elements simulations, considering various scenarios of carbonation and humidity. Results showed that, in spite of the high electrical resistivity of carbonated concrete, anodes with spacing of 0.45 m are enough to protect corroding reinforcement in most exposure conditions, even in thin parts of element. Estimated anode durations were of the order of several years or even decades; however, it was shown that also reinforcement in dry (carbonated or alkaline) concrete, which does not need to be protected, contributes to anode consumption. Although other aspects play a role on the performance of a cathodic protection system (such as the effectiveness of anode-encasing material and of electrical connection to reinforcement), the results obtained are supportive of a repair strategy based on the use of localised galvanic anodes and can be generalised to slender elements exposed to atmospheric conditions suffering carbonation induced corrosion

Investigation on the effect of supplementary cementitious materials on the critical chloride threshold of steel in concrete

open3noThe critical chloride threshold is a key parameter in the service life design of reinforced concrete structures exposed to chloride-bearing environments. This paper investigates the role of concrete composition, and particularly the effect of supplementary cementing materials, on the chloride threshold. To simulate real exposure conditions, ponding tests were carried out on reinforced concrete specimens with bars in free corrosion conditions and corrosion initiation was detected through corrosion potential and corrosion rate measurements. After two and a half years, the ponding was followed by an ageing period and the initiation of corrosion was further detected with anodic potentiostatic polarisation tests. Results of the tests showed several limitations of the approach based on chloride penetration and monitoring of free corrosion parameters to investigate the chloride threshold. In spite of this, a possible role of natural pozzolan and coal fly ash additions in leading to higher values of the chloride threshold and ground limestone in promoting lower values of the chloride threshold could be observed.Lollini, Federica; Redaelli, Elena; Bertolini, LucaLollini, Federica; Redaelli, Elena; Bertolini, Luc

Endoscopic Ear Surgery in Children

Endoscopic assistance is gradually gaining recognition in otology not only for office examinations but also during surgery. The first endoscopic surgical procedure that was started in our institution was endoscopic ventilation tube placement to manage children with stenotic and curved canals. Following this, endoscopy was used in all type I tympanoplasty and stage I cholesteatoma removals with the advantage of avoiding a postauricular or endaural approach. The last application of endoscopic assistance was to better visualize round window and scala tympani via posterior tympanotomy during cochlear implantation. There are several advantages in using endoscopes: the wide view obtained and the possibility to observe areas behind the angle with less invasiveness and its excellent resolution, in addition to its intense light and higher magnification that facilitates teaching and tutoring. The limits of endoscopic surgery are that one hand is always needed to hold the endoscope and the lack of a third dimension. Until miniaturization of 3D systems allow the possibility to work in the narrow external ear canal, in order to overcome the limitation that one hand is dedicated to the endoscope, we will describe the use of an endoscope holder in otologic procedures

Nitrogen fractionation in ammonia and its insights on nitrogen chemistry

Context. Observations of $\rm ^{14}N/^{15}N$ in the interstellar medium are becoming more frequent thanks to the increased telescope capabilities. However, interpreting these data is still puzzling. In particular, measurements of $\rm ^{14}N/^{15}N$ in diazenylium revealed high levels of anti-fractionation in cold cores. Aims. Furuya & Aikawa (2018), using astrophysical simulations coupled with a gas-grain chemical code, concluded that the $^{15}$N-depletion in prestellar cores could be inherited from the initial stages, when $\rm ^{14}N^{15}N$ is selectively photodissociated and 15N atoms deplete onto the dust grain, forming ammonia ices. We aim to test this hypothesis. Methods. We targeted three sources (the prestellar core L1544, the protostellar envelope IRAS4A, and the shocked region L1157-B1) with distinct degrees of desorption or sputtering of the ammonia ices. We observed the NH3 isotopologues with the GBT, and we inferred the $\rm ^{14}N/^{15}N$ via a spectral fitting of the observed inversion transitions. Results. $^{15}$NH3(1,1) is detected in L1544 and IRAS4A, whilst only upper limits are deduced in L1157-B1. The NH3 isotopic ratio is significantly lower towards the protostar than at the centre of L1544, where it is consistent with the elemental value. We also present the first spatially resolved map of NH3 nitrogen isotopic ratio towards L1544. Conclusions. Our results are in agreement with the hypothesis that ammonia ices are enriched in $^{15}$N, leading to a decrease of the $\rm ^{14}N/^{15}N$ ratio when the ices are sublimated into the gas phase for instance due to the temperature rise in protostellar envelopes. The ammonia $\rm ^{14}N/^{15}N$ value at the centre of L1544 is a factor of 2 lower than that of N2H+, suggesting that the dominant formation pathway is hydrogenation of N atoms on dust grains, followed by non-thermal desorption.Comment: Accepted for publication in A&A on 29/05/2

Design of polarization-insensitive superconducting single photon detectors with high-index dielectrics

In this paper, the design of superconducting-nanowire single-photon detectors which are insensitive to the polarization of the incident light is investigated. By using high-refractive-index dielectrics, the index mismatch between the nanowire and the surrounding media is reduced. This enhances the absorption of light with electric field vector perpendicular to the nanowire segments, which is generally hindered in this kind of detectors. Building on this principle and focusing on NbTiN nanowire devices, we present several easy-to-realize cavity architectures which allow high absorption efficiency (in excess of 90%) and polarization insensitivity simultaneously. Designs based on ultranarrow nanowires, for which the polarization sensitivity is much more marked, are also presented. Finally, we briefly discuss the specific advantages of this approach in the case of WSi or MoSi nanowires

The challenge of the performance-based approach for the design of reinforced concrete structures in chloride bearing environment

The performance-based approach, published by the International Federation for Structural Concrete (fib), was applied for the design of a RC element in a marine environment, with corrosion resistant reinforcement, to analyse the potentiality of the model as well as the possible reasons which limit its use. Results showed that the fib model allows to compare different solutions and to consider the benefits connected with the use of preventative measures. However the definition of reliable values for some input parameters, as the critical chloride threshold for corrosion resistant reinforcement, is demanded to the designer and this aspect clearly limits a widespread use

Corrosion of Steel in Concrete and Its Prevention in Aggressive Chloride-Bearing Environments

This keynote paper deals with the durability of reinforced concrete (RC) structures exposed to aggressive environments characterized by high concentration of chloride ions, namely, marine environments or the use of de-icing salts. The mechanism of chloride-induced corrosion of steel in concrete is introduced, and its influence on the service life of RC structures is analyzed. Factors affecting the time to corrosion initiation are described with regard to both concrete properties and environmental exposure conditions. Design approaches available for achieving durability targets associated with the design service life are analyzed, focusing on studies carried out by the authors in recent years at the mCD Concrete Durability lab of Politecnico di Milano, which were aimed at improving the protection provided to the steel bars by the concrete cover, investigating the advantages of using corrosion-resistant stainless steel bars and developing the electrochemical technique of cathodic prevention

Effects of nanosilica on compressive strength and durability properties of concrete with different water to binder ratios

The effects of the addition of different nanosilica dosages (0.5%, 1%, and 1.5% with respect to cement) on compressive strength and durability properties of concrete with water/binder ratios 0.65, 0.55, and 0.5 were investigated. Water sorptivity, apparent chloride diffusion coefficient, electrical resistivity, and carbonation coefficient of concrete were measured. The results showed that compressive strength significantly improved in case of water/binder = 0.65, while for water/binder = 0.5 no change was found. Increasing nanosilica content, the water sorptivity decreased only for water/binder = 0.55. The addition of 0.5% nanosilica decreased the apparent chloride diffusion coefficient for water/binder = 0.65 and 0.55; however, higher nanosilica dosages did not decrease it with respect to reference value. The resistivity was elevated by 0.5% nanosilica for all water/binder ratios and by 1.5% nanosilica only for water/binder = 0.5. The carbonation coefficient was not notably affected by increasing nanosilica dosages and even adverse effect was observed for water/binder = 0.65. Further information of microstructure was also provided through characterization techniques such as X-ray diffraction, thermal gravimetric analysis, mercury intrusion porosimetry, and scanning electron microscopy. The effectiveness of a certain nanosilica dosage addition into lower strength mixes was more noticeable, while, for the higher strength mix, the effectiveness was less

Modification of properties of reinforced concrete through nanoalumina electrokinetic treatment

An attempt was made to drift nanoalumina particles into concrete pores through electrokinetic treatment. An external electric current (current density = 3 A/m2) was applied for 3 and 15 days in reinforced concrete blocks toward steel reinforcement and microstructural characterizations (i.e. morphology observation and porosity analysis) were performed on concrete fragments of different depth from exposure surface. The morphology observation evidenced transport of nanoalumina from the exposure surface even reaching the rebar-concrete interface (up to 25–30 mm, in 15 days treatment). The porosity analysis of treated samples revealed that reduction of porosity of rebar interface was more pronounced as compared to the exposure surface and the treatment for 15 days was more beneficial for porosity refinement than treatment for 3 days. Effects of the electrokinetic NA treatment on strength of rebar-concrete interface were evaluated through pull-out test. The results showed that by increasing current density, bond strength of rebar-concrete interface increased