Endocrine disruptors and obesity

The purpose of this review is to summarise current evidence that some environmental chemicals may be able to interfere in endocrine regulation of energy metabolism and adipose tissue structure. Recent findings demonstrate that such endocrine disrupting chemicals, termed “obesogens”, can promote adipogenesis and cause weight gain. This includes compounds to which the human population is exposed in daily life through their use in pesticides/herbicides, industrial and household products, plastics, detergents, flame retardants and ingredients in personal care products. Animal models and epidemiological studies have shown that an especially sensitive time for exposure is in utero or the neonatal period. In summarising the actions of obesogens, it is noteworthy that as their structures are mainly lipophilic, their ability to increase fat deposition has the added consequence of increasing the capacity for their own retention. This has the potential for a vicious spiral not only of increasing obesity but also increasing retention of other lipophilic pollutant chemicals with an even broader range of adverse actions. This might offer an explanation as to why obesity is an underlying risk factor for so many diseases including cancer

L'identità dell'oratore antico, fra singolare e plurale

(L.S.,Premessa, pp. 67-70; Singolare e plurale, tra Eschine e Demostene, pp. 81-84)

Optimization of a cyclonic combustion chamber for the thermochemical conversion of alternative fuels

This work provides an insight into the influence of the design parameters, specifically the configuration of the outlet section, on the fluid dynamic field and residence times distribution of a cyclonic flow burner, designed to operate under Moderate or Intense Low oxygen Dilution (MILD) combustion conditions with alternative energy carriers. The investigated geometric parameters play a key role in determining the velocity pattern and mixing process of the reactant mixture, fluids residence time distribution and burned gas internal recirculation, by influencing the oxidation process efficiency and pollutant emissions. These latter characteristics are essential in the framework of the recent global energy transition toward renewable sources. Indeed, the intermittency of renewables sources requires the development of specific processes and technologies able to mitigate their inherent variability. Among them, chemical storage ensures large storage capacity for long period and with high efficiency, ensuring easy and safe transportation and storage. In this context, bio-derived alcohols and free carbon fuels such as ammonia and hydrogen have been identified as alternative energy carriers to efficiently storage the renewable energy. Nevertheless, the exploitation of these molecules poses some relevant challenges. The most considerable obstacles are related to the variable composition of the bio-derived products and the consequent lower heating value with respect to traditional hydrocarbon fuels. These aspects greatly limit the technologies capable of employing such energy carriers. Therefore, it is necessary to identify innovative thermochemical conversion technologies highly flexible with respect to the type and composition of the fuel, which ensure reduced pollutant emissions and the stability of the oxidation process for each required operational condition. In this respect, MILD combustion represents an efficient technology matching these issues. In this context, the obtained results allow to identify the appropriate design features of a cyclonic flow burner in order to ensure the complete conversion of the inlet charge and the effective process stabilization

Reactive Structures of Ammonia MILD Combustion in Diffusion Ignition Processes

Reactive structures have been analyzed, when ammonia is used as a fuel, in a steady 1D counterflow diffusion flame layer, mimicking diffusion ignition processes. The characterization has been carried out in a wide range of feeding parameters under Moderate or Intense Low-oxygen Dilution (MILD) combustion conditions. Both the Hot-Fuel-Diluted-Fuel (HFDF) and Hot-Oxidant-Diluted-Fuel (HODF) configurations were studied to analyze the main effects of the inlet feeding conditions on the oxidative structures. The reaction zone has been analyzed in terms of temperature and heat release profiles in the mixture fraction space for various ranges of inlet parameters, using a standard code and a validated chemical kinetic scheme. Several features of the reaction zone have been recognized as reported also in previous works for hydrocarbon flames. They were used as discriminative for the achievement of various combustion regimes. In particular, the flame thickening process and the absence of correlation between the maximum heat release and the stoichiometric mixture fraction were analyzed to build maps of behaviors. The latter were reported on an inlet preheating level-temperature increase plane for fixed values of the bulk strain rate and system pressures. Another relevant feature previously reported with hydrocarbons in the literature, in Hot Diluted Diffusion Ignition (HDDI) processes under MILD conditions, was the pyrolysis depression. The latter characteristic has been not observed when ammonia is used as a fuel, for the operative conditions here investigated. Indeed, the heat release profiles do not show the presence of negative heat release regions. The results obtained for the HFDF configuration are strongly dependent on the system pressure level. Finally, the HODF condition has been also analyzed for ammonia at the atmospheric pressure. Boundaries of the combustion regimes and reactive structure features showed several differences between HFDF and HODF cases with respect to the inlet parameters

Influence of water addition on MILD ammonia combustion performances and emissions

The global energy shift towards the exploitation of Renewable Energy Sources requires the development of proper energy storage and back-up technologies to deal with their intermittency and seasonality. Renewable Energy chemical storage offers the possibility of efficiently storing large amounts of energy for long time. On the other hand, ammonia is increasingly considered a feasible alternative to the use of hydrogen, due to the existence of already well assessed production technologies and transport infrastructures. However, the exploitation of ammonia as an energy carrier poses some relevant challenges. The most relevant ones concern combustion stability and NO x emissions, when ammonia is burned in traditional conditions. A promising approach to ensure combustion stability while containing NO x emissions relies on the shift from traditional to new combustion modes. MILD Combustion has been proven as a reliable alternative to reach these targets. At the same time, water addition to reactants is a well-known strategy that promote DeNO x routes in fossil fuel combustion. In this work, combustion of ammonia-air mixtures assisted by water is studied in a cyclonic burner exercised under MILD operative conditions, to evaluate the effect of water addition on NO x emissions and process stability. The analyses were carried out in premixed and non-premixed feeding conditions. Results highlighted that water addition to the reactant mixture may represent a very simple and efficient solution in determining the reduction of NO x emissions in ammonia combustion, especially in fuel-lean conditions. Moreover, the comparison between premixed and non-premixed configuration shows that it is possible to enhance the process performance through a simultaneous optimization of the burner internal flow-field and reactants injection strategies

Alcohols as energy carriers in MILD Combustion

Among the liquid fuels supporting the decarbonization of the energy conversion chain, alcohols play a key role. Mainly considered for engine application, their use in stationary systems designed for power generation is receiving considerable attention but requires further investigation. This work aims at demonstrating the feasibility of thermochemical conversion of lowmolecular- weight alcohols, methanol, ethanol, and 1-butanol, in a small-scale unit exercised under moderate or intense low-oxygen dilution combustion conditions. The highly recirculated flow field configuration allows for the stabilization of the process over a wide range of reactor temperatures. The experimental campaign is carried out by varying the mixture equivalence ratio and the thermal power. The burner was exercised with different gas feeding configurations, namely, premixed and non-premixed. Experimental results are reported in terms of operational temperatures and pollutant emissions (CO and NOx). For all of the fuels and thermal power, it was possible to reach NOx levels lower than 20 ppm and CO below 40 ppm for a wider range of the mixture equivalence ratio than hydrocarbon fuels. Despite similarities in the temperature profiles and CO emissions, NOx levels increase with the complexity of the alcohol molecules and their distribution is also a function of the injection strategy. Simulations in a perfectly stirred reactor and in a counterflow diffusion flame were performed to provide insights into the key factors controlling the NOx emission levels and distribution. Numerical results with a perfectly stirred reactor model show the role of NOx chemistry in determining the different emission levels of the three alcohols. On the other hand, simulations with a counterflow diffusion flame suggest that the separate reactant supply to the combustion chamber represents the key parameter in determining the experimental NOx distribution in the non-premixed mode

Robin George Collingwood e la formazione estetica I Volume

L'analisi della formazione estetica è un particolare della produzione dell'idealismo inglese, interconnesso all'italiano, che è stato affrontato dagli autori in molti diversi approfondimenti. Il convegno che ha raccolto i saggi è stato frequentato da altri autori ancora non editi nel primo volume

MILD Combustion and Biofuels: A Minireview

Even in the presence of the formidable growth of renewable energy sources, advanced combustion processes have and will continue to have an irreplaceable role as a driving force for energy market. This is indeed motivated by the same huge amount of energy that can be conveniently stored in the form of energy carriers, made available from the renewable sources. The coupling of the appropriate combustion conversion technology with locally available biofuels certainly is among the most effective solutions, now on the table, to face the decarbonization challenge. In this framework, moderate or intense low oxygen dilution (MILD) combustion is among the best candidates to support the transition toward the net zero emission target. Indeed, due to its inherent features, it is highly fuel flexible and efficient, allowing for the utilization of whatever energy carrier can be considered in the decarbonization strategy. It is also characterized by an inherent low or absent pollutant emission. The novelty of this minireview is to highlight the relevance of the kinetics involved in MILD combustion processes with particular focus on biofuels, identifying invariant temperatures, relevant for process stabilization for any energy carrier. A critical evaluation of advantages and drawbacks of the use of raw bioliquids in MILD combustion conditions is reported. Then, challenges, open questions, and future perspectives on the use of biofuel in MILD combustion are discussed