A hydrogel film, poly-3,4-ethylenedioxythiophene (PEDOT):polystyrenesulfonate (PSS), containing an ionic liquid, is used as an air-cathode for a metal-air battery and its performance is investigated. ...This work presents the development of the air-cathode and the characterization of its physical, chemical and mechanical properties. Moreover, in view of wearable batteries, these air-cathodes are implemented within a flexible aluminium-air battery. It contains an aluminium anode, an electrolyte made of cellulose paper imbibed with an aqueous sodium chloride solution and the PEDOT:PSS air-cathode. Characterisation tests showed that the ionic liquid did not change the air-cathode chemically, while the electric conductivity increased considerably. The anode has an acceptable purity and was found to be resistant against self-corrosion. Discharge tests showed operating voltages up to 0.65 V, whereas two batteries in series could deliver up to 1.3 V at a current density of 0.9 mA cm
for almost a day, sufficient for monitoring and medical devices. Several discharge tests with current densities from 0.25 up to 2.5 mA cm
have presented operating lifetimes from 10 h up until over a day. At a current density of 2.8 mA cm
, the operating voltage and lifetime dropped considerably, explained by approaching the limiting current density of about 3 mA cm
, as evidenced by linear sweep voltammetry. The batteries showed high specific energies up to about 3140 Wh kg
. Mechanical tests revealed a sufficient stretchability of the air-cathode, even after battery discharge, implying an acceptable degree of wearability. Together with the reusability of the air-cathode, the battery is a promising route towards a low-cost viable way for wearable power supply for monitoring medical devices with long lifetimes and high specific energies. Optimization of the air-cathode could even lead to higher power applications.
In the process of tissue engineering, several types of stresses can influence the outcome of tissue regeneration. This outcome can be understood by designing hydrogels that mimic this process and ...studying how such hydrogel scaffolds and cells behave under a set of stresses. Here, a hydrogel formulation is proposed to create biomimetic scaffolds suitable for fibroblast cell culture. Subsequently, we examine the impact of external stresses on fibroblast cells cultured on both solid and porous hydrogels. These stresses included mechanical tension and altered-gravity conditions experienced during the 83rd parabolic flight campaign conducted by the European Space Agency. This study shows distinct cellular responses characterized by cell aggregation and redistribution in regions of intensified stress concentration. This paper presents a new biomimetic hydrogel that fulfills tissue-engineering requirements in terms of biocompatibility and mechanical stability. Moreover, it contributes to our comprehension of cellular biomechanics under diverse gravitational conditions, shedding light on the dynamic cellular adaptations versus varying stress environments.
In the last years, even more attention was paid to the alternative fuels that allow both reducing the fossil fuel consumption and the pollutant emissions. Gaseous fuels like methane and hydrogen are ...the most interesting in terms of engine application. This paper reports a comparison between methane and different methane/hydrogen mixtures in a single-cylinder Port Fuel/Direct Injection spark ignition (PFI/DI SI) engine operating under steady state conditions. It is representative of the gasoline engine for automotive application. Engine performance and exhaust emissions were evaluated. Moreover, 2D-digital cycle resolved imaging was performed with high spatial and temporal resolution in the combustion chamber. In particular, it allows characterizing the combustion by means of the flame propagation in terms of mean radius and velocity. Moreover, the interaction of turbulence with the local flame was evaluated.
For both the engine configurations, it was observed that the addition of hydrogen results in a more efficient combustion, even though the engine configuration plays an important role. In PFI mode, the lower density of hydrogen causes a lower energy input. In DI mode, instead, the larger hydrogen diffusivity counteracts the charge stratification especially for larger hydrogen content.
•The effect of hydrogen on methane combustion was investigated in an optical PFI/DI SI engine.•The effect of hydrogen addition for PFI and DI configurations was evaluated on the same engine.•The flame front propagation was characterized by means of 2-D digital imaging.
Reversible high temperature solid oxide cells (rSOC) can be operated both in the fuel cell (SOFC) and the electrolysis mode (SOEC). This specificity is a promising way to either store intermittent ...renewable energy surpluses by producing H2, or generate electricity from H2 or any other fuel locally available (CH4, biogas) when demand overtakes the local production. Therefore, rSOC technology could reinforce autonomy and flexibility in buildings, eco‐districts, up to industrial sites and local energy grids powered by intermittent renewable energies. Such a storage solution complements batteries, displays flexible energy storage durations, from a few hours up to seasonal cycles, and allows decorrelating power and storage capacity. Nonetheless, experiments are needed to assess whether rSOC systems can accommodate the surrounding environment and switch rapidly between various power levels and operating modes.
An rSOC system has been built and its ability to operate in both electrolysis and fuel cell modes has been demonstrated. The present work is focused on transitioning between 3 operating modes (SOEC, SOFC operated in H2, SOFC operated in CH4), each displaying 3 power levels. The results show that all transition cycles could be done in 3 to 10 min without negatively affecting short term stack performances.
The energy crisis and environmental issues make the alternative fuels, both liquid and gaseous, even more attractive because of their potentiality in reducing the fuel consumption and the pollutant ...emissions. Ethanol is the most promising alternative liquid fuel for spark ignition engines. It has a higher octane number, which provides good anti-knock characteristics and in the possibility to work with higher compression ratios, so improving the engine efficiency. The higher heat of vaporization compared to gasoline leads to an increased power output. Moreover, the larger oxygen content provides a more complete combustion and therefore reduced emissions. Among gaseous fuels, methane is considered one of the most interesting. It has wider flammable limits and better anti-knock properties than gasoline. Moreover, it is characterized by lower CO2 emissions. On the other hand, the slow flame propagation speed and its poor lean-burn capability produce lower engine power output with respect to gasoline. The addition of a high burning velocity fuel, such as hydrogen, allows to improve the combustion process in terms of burning velocity and extend the lean operation limit. The objective of this paper is the analysis of the effect of different fuels on the engine performance and emissions. Experimental investigations were carried out in an optically accessible small single-cylinder, spark ignition four-stroke engine. It was equipped with the cylinder head of a Port Fuel Injection commercial 244 cc engine. The engine was fueled with gasoline, ethanol, methane and a blend of hydrogen in methane. Optical measurements were performed to analyze the combustion process with high spatial and temporal resolution. In particular, the optical techniques based on 2D-digital imaging were used to follow the flame propagation in the combustion chamber. UV–visible spectroscopy allows the detection of chemical markers of the combustion process such as the radicals OH* and CH*. The exhaust emissions were characterized by means of gaseous analyzers. The measurements were performed at steady state conditions.
•Optical analysis of the effect of liquid/gaseous biofuels on combustion process.•Ethanol combustion is less efficient at low engine speed and load.•Hydrogen addition improves methane combustion process.
•The influence of natural gas composition is investigated.•Real-time methane/propane fuel mixtures were realized.•IMEP, HRR and MBF were used to evaluate the effects on engine performance.•Gaseous, ...greenhouse and Particulate emissions were studied.•The propane content strongly influenced performance and emissions.
In vehicles fueled with compressed natural gas, a variation in the fuel composition can have non-negligible effects on their performance, as well as on their emissions. The present work aimed to provide more insight on this crucial aspect by performing experiments on a single-cylinder port-fuel injected spark-ignition engine. In particular, methane/propane mixtures were realized to isolate the effects of a variation of the main constituents in natural gas on engine performance and associated pollutant emissions. The propane volume fraction was varied from 10 to 40%. Using an experimental procedure designed and validated to obtain precise real-time mixture fractions to inject directly into the intake manifold. Indicative Mean Effective Pressure, Heat Release Rate and Mass Burned Fraction were used to evaluate the effects on engine performance. Gaseous emissions were measured as well. Particulate Mass, Number and Size Distributions were analyzed with the aim to identify possible correlations existing between fuel composition and soot emissions. Emissions samples were taken from the exhaust flow, just downstream of the valves. Opacity was measured downstream the Three-Way Catalyst. Three different engine speeds were investigated, namely 2000, 3000 and 4000rpm. Stoichiometric and full load conditions were considered in all tests. The results were compared with pure methane and propane, as well as with natural gas. The results indicated that both performance and emissions were strongly influenced by the variation of the propane content. Increasing the propane fraction favored more complete combustion and increased NOx emissions, due to the higher temperatures. In all tests, natural gas showed the highest PN values. At high speeds, adding propane increased the number of particles between 5 and 30nm, highlighting the relevance of the ultrafine particles. Smaller differences were recorded at low speeds.
High Temperature Steam Electrolysis (HTSE), based on solid oxide electrolysis cells (SOE) is a promising way to produce massively hydrogen with high efficiencies. This technology also allows ...producing syngas (H2 + CO) by co-electrolyzing a mix of steam and CO2. This syngas constitutes the basis to obtain further synthetic fuels. For both HTSE and co-electrolysis, durability and cost are still key points, but additionally for co-electrolysis the outlet H2/CO gas composition has to be tailored to fit with the targeted fuels. Previous works have been carried out to develop a stack design suitable for both applications. Here experiments at stack level in both electrolysis and co-electrolysis modes have been carried out. A 10-cell stack and a 25-cell stack have been tested in electrolysis mode, respectively producing 0.6 Nm3/h and 1.7 Nm3/h of hydrogen at 800 °C below the thermoneutral voltage (1.3 V) for all the cells and a steam conversion around 50%, with a small scattering between the different cells. Gas tightness of the stacks has also been evaluated. Moreover, the operation in co-electrolysis has been validated. Finally a cost analysis of this stack design has been performed and shows all the economical potentialities of this technology.
•A high-performance solid oxide electrolyser stack is presented and tested.•SOEC from single cell to 25-cells stack results are presented and discussed. The thermal management is quantified.•H2O + CO2 co-electrolysis results with syngas composition analysis are also presented.•A cost analysis of this design is performed.•A comparison to other electrolysis technologies, as a function of the electricity price, confirms the potential of SOEC.
Purpose
During the COVID-19 pandemic, elective thyroid surgery is experiencing delays. The problem is that the COVID-19 pandemic is ongoing. The research purposes were to systematically collect the ...literature data on the characteristics of those thyroid operations performed and to assess the safety/risks associated with thyroid surgery during the COVID-19 pandemic.
Methods
We used all the procedures consistent with the PRISMA guidelines. A comprehensive literature in MEDLINE (PubMed) and Scopus was made using ‘‘Thyroid’’ and “coronavirus” as search terms.
Results
Of a total of 293 articles identified, 9 studies met the inclusion criteria. The total number of patients undergoing thyroid surgery was 2217. The indication for surgery was malignancy in 1347 cases (60.8%). Screening protocols varied depending on hospital protocol and maximum levels of personal protection equipment were adopted. The hospital length of stay was 2–3 days. Total thyroidectomy was chosen for 1557 patients (1557/1868, 83.4%), of which 596 procedures (596/1558, 38.3%) were combined with lymph node dissections. Cross-infections were registered in 14 cases (14/721, 1.9%), of which three (3/721, 0.4%) with severe pulmonary complications of COVID-19. 377 patients (377/1868, 20.2%) had complications after surgery, of which 285 (285/377, 75.6%) hypoparathyroidism and 71 (71/377, 18.8%) recurrent laryngeal nerve injury.
Conclusion
The risk of SARS-CoV-2 transmission after thyroid surgery is relatively low. Our study could promote the restart of planned thyroid surgery due to COVID-19. Future studies are warranted to obtain more solid data about the risk of complications after thyroid surgery during the COVID-19 era.
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