On the Use of Quantum Chemistry for the Determination of Propagation, Copolymerization, and Secondary Reaction Kinetics in Free Radical Polymerization

Throughout the last 25 years, computational chemistry based on quantum mechanics has been applied to the investigation of reaction kinetics in free radical polymerization (FRP) with growing interest. Nowadays, quantum chemistry (QC) can be considered a powerful and cost-effective tool for the kinetic characterization of many individual reactions in FRP, especially those that cannot yet be fully analyzed through experiments. The recent focus on copolymers and systems where secondary reactions play a major role has emphasized this feature due to the increased complexity of these kinetic schemes. QC calculations are well-suited to support and guide the experimental investigation of FRP kinetics as well as to deepen the understanding of polymerization mechanisms. This paper is intended to provide an overview of the most relevant QC results obtained so far from the investigation of FRP. A comparison between computational results and experimental data is given, whenever possible, to emphasize the performances of the two approaches in the prediction of kinetic data. This work provides a comprehensive database of reaction rate parameters of FRP to assist in the development of advanced models of polymerization and experimental studies on the topic

All-Optical Reinforcement Learning in Solitonic X-Junctions

L'etologia ha dimostrato che gruppi di animali o colonie possono eseguire calcoli complessi distribuendo semplici processi decisionali ai membri del gruppo. Ad esempio, le colonie di formiche possono ottimizzare le traiettorie verso il cibo eseguendo sia un rinforzo (o una cancellazione) delle tracce di feromone sia spostarsi da una traiettoria ad un'altra con feromone più forte. Questa procedura delle formiche possono essere implementati in un hardware fotonico per riprodurre l'elaborazione del segnale stigmergico. Presentiamo qui innovative giunzioni a X completamente integrate realizzate utilizzando guide d'onda solitoniche in grado di fornire entrambi i processi decisionali delle formiche. Le giunzioni a X proposte possono passare da comportamenti simmetrici (50/50) ad asimmetrici (80/20) utilizzando feedback ottici, cancellando i canali di uscita inutilizzati o rinforzando quelli usati.Ethology has shown that animal groups or colonies can perform complex calculation distributing simple decision-making processes to the group members. For example ant colonies can optimize the trajectories towards the food by performing both a reinforcement (or a cancellation) of the pheromone traces and a switch from one path to another with stronger pheromone. Such ant's processes can be implemented in a photonic hardware to reproduce stigmergic signal processing. We present innovative, completely integrated X-junctions realized using solitonic waveguides which can provide both ant's decision-making processes. The proposed X-junctions can switch from symmetric (50/50) to asymmetric behaviors (80/20) using optical feedbacks, vanishing unused output channels or reinforcing the used ones

A Differential Mechatronic Device: Design, Simulation and Experimental Results

Differential mechanisms are widely studied in literature, from a theoretical viewpoint and for applicative reasons. A differential mechanism is a mechanical system with one or more output motions resulting from the combination of different input motions acting on the same degree of freedom. In this work, we point the attention on planar differential systems (a monoaxis and a Cartesian device) composed by belts and pulleys. Particularly the Vernier effect is used to realize high-speed and highaccuracy devices with low-cost components. Simplified models of these two systems are presented to show the main kinematic and dynamic features. An advanced model is then realized for the Cartesian device with the aid of the Dymola software and simulation results are compared with the expected ones from the simplified model. The control of the system is realized with three PI systems (proportionalintegrative) optimized via an adaptive logic. Finally early experimental results are presented only for the monoaxis system

A safe production process of alkylene oxide from alkylene carbonates

Alkylene oxides of low molecular weight, ethylene, and propylene oxides, are widely used in industry. They are used to produce other chemicals and products such as solvents, surfactants, antifreeze, adhesives, polyurethane foams, and pharmaceuticals. They are also used as fumigants in agricultural products and as sterilants for medical equipment and supplies. Unfortunately, it is worth noting that alkylene oxides also possess several physical and health hazards that merit special attention. They are flammable and explosive and their storage and transportation warrant stringent safety rules. The obvious solution to reduce the risk is to generate them from intermediate safety materials only when and only where they are necessary. The literature suggests that correspondent carbonates are very stable precursors. The scope of our study is that of identifying the optimal conditions to generate ethylene and propylene oxide at the moment just before their reaction and uses. The patent deals with some equipment and process conditions that guarantee a fast and reliable dissociation of carbonates in their correspondent oxides. The natural output of the patent is a unit able to provide the dangerous material in situ, under controlled conditions. As a result, all the risks related to transportation and storage are eliminated

Methane Reforming with H2S and Sulfur for Hydrogen Production: Thermodynamic Assessment

Nowadays, most ofthe hydrogen is obtained from fossil fuels. Atthe same time, the effort and resources dedicated to the developmentof sustainable hydrogen manufacturing processes are rapidly increasingto promote the energy transition toward renewable sources. In thisdirection, a potential source of hydrogen could be hydrogen sulfide,produced as a byproduct in several processes, and in particular inthe oil extraction and refinery operations. Methane reforming usingH(2)S has recently attracted much interest for its economicand environmental implications. Its conversion, in fact, providesa viable way for the elimination of a hazardous molecule, producinga high-added value product like hydrogen. At the same time, some ofthe still open key aspects of this process are the coke depositiondue to thermal pyrolysis of methane and the process endothermicity.In this work, the methane reforming with H2S by co-feedingsulfur is investigated through a detailed thermodynamic analysis asa way to alleviate the critical aspects highlighted for the process.A parametric analysis was conducted to assess the best thermodynamicconditions in terms of pressure, temperature, and feed composition.Changing the sulfur, H2S, and methane feed compositioncan enhance the system by improving the hydrogen production yield,reducing the carbon and sulfur deposition, increasing the H2S removal efficiency, and reducing the necessary thermal duty

Thermo-responsive polymers as surface active compounds: A review

The great versatility and controllable properties that characterize polymeric materials allowed their spreading to many different areas. In the last years, this outstanding adaptability was even amplified by the introduction of smart polymers, i.e. materials able to sharply and often reversibly change their physico-chemical properties in response to external stimuli. In particular, the possibility of applying thermal stimuli in a controlled and simple way, coupled with the natural occurrence of thermal gradients, made thermo-responsive polymers particularly appealing, as they allowed to conceive applications that were not even imaginable for traditional materials. In this review we discuss the great potentialities of thermo-responsive polymers when used to functionalize a target surface or interface. The discussion will cover significant areas of interest where this class of materials has been employed, including cell culture, chromatography, colloidal stabilization and enhanced oil recovery. Many examples from the literature are reported in order to present the state of the art, the main advantages of this technology over conventional materials and the expected future developments. Moreover, some successful examples highlighting the innovative functionalities achievable by these active surfaces are presented

Chemical recycling of polyethylene terephthalate (PET) to monomers: Mathematical modeling of the transesterification reaction of bis(2-hydroxyethyl) terephthalate to dimethyl terephthalate

The accumulation of plastic waste in the environment is making recycling a compelling issue, particularly for polyethylene terephthalate (PET), used in products with a short shelf-life. An appealing route to chemical recycling of PET is glycolysis, leading to bis(2-hydroxyethyl) terephthalate (BHET). Its subsequent transesterification with methanol to dimethyl terephthalate (DMT) is crucial for the recovery of polymer-grade monomers. To favor the industrial applicability of this process, this work investigates the influence of three main parameters, i.e. the methanol to ethylene glycol molar ratio, the solvent to oligomers molar ratio and the mass fraction of the catalyst, on the transesterification of BHET to DMT. A kinetic model has been proposed, and the reaction rates evaluated by comparison with the experimental data. The model was used to predict the performances of the process in a wide range of operating conditions, in order to establish the optimal ones for high yield to DMT

Disaster Risk Management of Cultural Heritage Sites in Albania.

UNESCO has a vital role to play in constructing a global culture of disaster preparedness and mitigation, building in the minds of people a Disaster Risk Management of Cultural Heritage Sites in Albania culture of resilience to risk, promoting awareness, education and capacity and foremost a different way to approach the domain of Disaster Risk Reduction (DRR) and preparedness. UNESCO is also the secretariat of the 1972 World Heritage Convention, of which the properties have recently been the focus of substantial advancement in securing better capacity in risk management and reduction. Since UNESCO is engaged in important actions for the protection of cultural heritage it implements several projects in post disaster scenarios. This book has been elaborated as a final outcome of the project \u201cNatural Risk Preparedness and Mitigation - Building capacity in the field of risk mitigation for Cultural Heritage properties in Albania\u201d during the period 2011-2013. The project aimed to streamline disaster risk management in the Country, using its World Heritage properties as demonstration sites. The project was conceived to assist the country in order to enhance its capacity for Disasters Risk Management (DRM) and advancement in seismological and geological vulnerability of Cultural Heritage properties

Optogalvanic Signals From Argon Metastables In A Rf Glow-Discharge

Laser optogalvanic (LOG) signals at 667.7, 751.5, and 696.5 nm from the 3 P 1 and 3 P 2 levels of Ar were studied at a pressure of 250 mTorr in a rf glow discharge. Signals with unexpected signs and time dependences were found. The results are interpreted as being due to radiative trapping effects and collisional mixing between resonance and metastable levels. An average electron energy of 2.1 eV is derived from modeling the data