293 research outputs found

    A conformal field theory description of magnetic flux fractionalization in Josephson junction ladders

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    We show how the recently proposed effective theory for a Quantum Hall system at "paired states" filling v=1 (Mod. Phys. Lett. A 15 (2000) 1679; Nucl. Phys. B641 (2002) 547), the twisted model (TM), well adapts to describe the phenomenology of Josephson Junction ladders (JJL) in the presence of defects. In particular it is shown how naturally the phenomenon of flux fractionalization takes place in such a description and its relation with the discrete symmetries present in the TM. Furthermore we focus on closed geometries, which enable us to analyze the topological properties of the ground state of the system in relation to the presence of half flux quanta.Comment: 16 pages, 2 figure, Latex, revised versio

    Two steps one pot process for the conversion of dimethylfuran to pyrrole compounds with almost null E factor

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    The replacement of the oil-based chemicals with those derived from biomasses is one of the most exciting challenges of the last decades. For example, 1,4-dicarbonyl compounds have a great importance in chemical synthesis, thanks to their high chemoselectivity and there is an increasing interest for preparing them from biomasses. In particular, 2,5-hexanedione could be synthesized starting from lignocellulosic sources, through the acid-ring opening reaction of 2,5-dimethylfuran as the bio-based feedstock.[1] The reaction of 2,5-hexanedione and a generic primary amine leads to pyrrole compounds. Many examples have been reported by some of the authors.[2] In this work a sustainable process for the preparation of pyrrole compounds starting from a bio-based reagent has been developed. The selected starting material was 2,5-dimethyl furan. In this work, the ring opening reaction of 2,5-dimethylfuran was optimized by tuning parameters such as the amount of water, type and amount of acid, time and temperature. 2,5-hexanedione was obtained with a high yield (95%) without the need of purification. Then, different primary amines, in particular biosourced, have been used to prepare a variety of pyrrole compounds, with high yield (at least 90%) and with high carbon efficiency, without producing waste. The pyrrole compounds have then been used for the functionalization of a nanosized graphite, promoting the exfoliation to few layers graphene

    Topological order in Josephson junction ladders with Mobius boundary conditions

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    We propose a CFT description for a closed one-dimensional fully frustrated ladder of quantum Josephson junctions with Mobius boundary conditions, in particular we show how such a system can develop topological order. Such a property is crucial for its implementation as a "protected" solid state qubit.Comment: 14 pages, 3 figures, to appear in JSTA

    A bio-sourced molecule as carbon black coupling agent in rubber compounds with low hysteresis

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    The prime application of rubber composites is represented by tire compounds. To achieve the desired tire performances an equilibrium between dynamic rigidity and hysteresis must be acquired. Amorphous precipitated silica is the preferred reinforcing filler to have low energy dissipations and thus low fuel consumption. Indeed, silica is characterized by nano dimensions and by the possibility of establishing chemical bonds with rubber chains allowing the achievement of high hysteresis at low temperatures, to promote wet traction, and low hysteresis at medium-high temperatures, for low fuel consumption. Carbon black (CB) is the main filler for tire compounds, but it does not have functional groups able to promote chemical bonds with the rubber matrix, though it would be highly desirable. In this work, a pyrrole compound (PyC) containing a thiol group, and which can be synthesized starting from bio-based building blocks was used to functionalize CB by the socalled “pyrrole methodology”. The thiol group was expected to react with the sulphurbased crosslinking system and/or with rubber chains, thus forming strong bonds with the rubber matrix. Results The synthesis of the PyC and the functionalization reaction were characterized by high atom efficiency. A poly(styrene-co-butadiene) copolymer from anionic solution polymerization was used as the main rubber for the compound preparation. The crosslinked composite material filled with functionalized CB revealed substantial improvements with respect to the composite with pristine CB, in particular: high rigidity and low hysteresis at high temperature. Composite properties were even comparable to those of silica-based rubber composites. The formation of the expected rubber-filler chemical bond via the thiol group of the selected PyC was confirmed studying such functionalizing agent in a squalene-based model compound. The results here reported pave the way to CB-based rubber composites with a low environmental impact

    UV irradiated graphene-based nanocomposites: Change in the mechanical properties by local harmoniX atomic force microscopy detection

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    Epoxy based coatings are susceptible to ultra violet (UV) damage and their durability can be significantly reduced in outdoor environments. This paper highlights a relevant property of graphene-based nanoparticles: Graphene Nanoplatelets (GNPs) incorporated in an epoxy-based free-standing film determine a strong decrease of the mechanical damages caused by UV irradiation. The effects of UV light on the morphology and mechanical properties of the solidified nanocharged epoxy films are investigated by Atomic Force Microscopy (AFM), in the acquisition mode "HarmoniX." Nanometric-resolved maps of the mechanical properties of the multi-phase material evidence that the incorporation of low percentages, between 0.1% and 1.0% by weight, of graphene nanoplatelets (GNPs) in the polymeric film causes a relevant enhancement in the mechanical stability of the irradiated films. The beneficial effect progressively increases with increasing GNP percentage. The paper also highlights the potentiality of AFM microscopy, in the acquisition mode "HarmoniX" for studying multiphase polymeric systems

    Recent developments in hazardous pollutants removal from wastewater and water reuse within a circular economy

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    Data availability: The authors declare that the data supporting the findings of this study are available within the manuscript. Further data can be requested (if need be) by contacting the corresponding author.Copyright © The Author(s) 2022. Recent advances in wastewater treatment processes have resulted in high removal efficiencies for various hazardous pollutants. Nevertheless, some technologies are more suitable for targeting specific contaminants than others. We comprehensively reviewed the recent advances in removing hazardous pollutants from industrial wastewater through membrane technologies, adsorption, Fenton-based processes, advanced oxidation processes (AOP), and hybrid systems such as electrically-enhanced membrane bioreactors (eMBRs), and integrated eMBR-adsorption system. Each technology’s key features are compared, and recent modifications to the conventional treatment approaches and limitations of advanced treatment systems are highlighted. The removal of emerging contaminants such as pharmaceuticals from wastewater is also discussed.Khalifa University through the Center for Membranes and Advanced Water Technology (CMAT), under grant number RC2-2018-009
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