L’articolo s’interroga sullo spazio del comico in Mimesis, saggio che poggia uno dei suoi assi portanti sul trattamento serio, tragico e problematico del quotidiano. Inserendo Auerbach nel suo ...orizzonte ideologico e ricostruendo brevemente la sua genealogia intellettuale, l’analisi indaga le ragioni che hanno portato l’autore a considerare il comico come la “forma” che impedisce l’emergere della problematicità realistica. Dopo una discussione su due problemi di fondo (uno semiologico, uno storico-letterario), l’articolo si sofferma sui capitoli di Mimesis in cui Auerbach tratta il comico – capitoli che spesso si rivelano essere i più utili per capire il suo metodo e la sua filosofia della storia.
Direct C–H bond activation is an important reaction in synthetic organic chemistry. This methodology has the potential to simplify reactions by avoiding the use of prefunctionalized reagents. ...However, selectivity, especially site selectivity, remains challenging. Sequential reactions, in which different molecules or groups are combined in an ordered sequence, represent a powerful tool for the construction of complex molecules in a single operation. We have discovered and developed a synthetic methodology that combines selective C–H bond activation with sequential reactions. This procedure, which is now known as the “Catellani reaction”, enables the selective functionalization of both the ortho and ipso positions of aryl halides. The desired molecules are obtained with high selectivity from a pool of simple precursors. These molecules are assembled under the control of a palladacycle, which is formed through the joint action of a metal (Pd) and an olefin such as norbornene. These two species act cooperatively with an aryl halide to construct the palladacycle, which is formed through ortho-C–H activation of the original aryl halide. The resulting complex acts as a scaffold to direct the reaction (via Pd(IV)) of other species, such as alkyl or aryl halides and amination or acylation agents, toward the sp2 C–Pd bond. At the end of this process, because of steric hindrance, the scaffold is dismantled by norbornene extrusion. Pd(0) is cleaved from the organic product through C–C, C–H, C–N, C–O, or C–B coupling, in agreement with the well-known reactivity of aryl-Pd complexes. The cycle involves Pd(0), Pd(II), and Pd(IV) species. In particular, our discovery relates to alkylation and arylation reactions. Recently, remarkable progress has been made in the following areas: (a) the installation of an amino or an acyl group at the ortho position of aryl halides, (b) the formation of a C–B bond at the ipso position, (c) the achievement of meta-C–H bond activation of aryl rings bearing a chelating directing group by Pd(II)/Pd(IV)/norbornene catalysis, and (d) the activation of N–H and C–H bonds in sequence for indole 2-alkylation. In this Account, we explain the main features of this methodology, describe its synthetic potential, and illustrate some remarkable progress that has been made, emphasizing the most recent developments and applications in total synthesis.
A Review of Dielectric Elastomer Generator Systems Moretti, Giacomo; Rosset, Samuel; Vertechy, Rocco ...
Advanced intelligent systems,
October 2020, 2020-10-00, 20201001, 2020-10-01, Volume:
2, Issue:
10
Journal Article
Peer reviewed
Open access
Dielectric elastomer generator systems (DEGSs) are a class of electrostatic soft‐transducers capable of converting oscillating mechanical power from different sources into usable electricity. Over ...the past years, a diversity of DEGSs has been conceived, integrated, and tested featuring diverse topologies and implementation characteristics tailored on different applications. Herein, the recent advances on DEGSs are reviewed and illustrated in terms of design of hardware architectures, power electronics, and control, with reference to the different application targets, including large‐scale systems such as ocean wave energy converters, and small‐scale systems such as human motion or ambient vibration energy harvesters. Finally, challenges and perspectives for the advancement of DEGSs are identified and discussed.
Dielectric elastomer generator systems (DEGSs) take advantage of electrostatic soft‐transducers to convert oscillating mechanical power into usable electricity. Over the past years, a diversity of DEGSs has been conceived with characteristics tailored to harvest energy from different sources such as ocean waves, human motion, and vibrations. Herein, an overview of the status of DEGS technology as of 2020 is provided.
Laser-induced graphene (LIG) emerged as one of the most promising materials for flexible functional devices. However, the attempts to obtain LIG onto elastomeric substrates never succeed, hindering ...its full exploitation for stretchable electronics. Herein, a novel polymeric composite is reported as a starting material for the fabrication of graphene-based electrodes by direct laser writing. A polyimide (PI) powder is dispersed into the poly(dimethylsiloxane) (PDMS) matrix to achieve an easily processable and functional elastomeric substrate, allowing the conversion of the polymeric surface into laser-induced graphene (LIG). The mechanical and electrical properties of the proposed material can be easily tuned by acting on the polyimide powder concentration. The reported procedure takes advantage from the simple casting process, typical of silicone elastomer, allowing to produce electrodes conformable to any kind of shape and surface as well as complex three-dimensional structures. Electrochemical capacitors and strain gauges are selected as flexible prototypes to demonstrate the multifunctional properties of the obtained LIG on the PDMS/PI composite substrate.
A hybrid aerogel, composed of MoS2 sheets of 1T (distorted octahedral) and 2H (trigonal prismatic) phases, finely mixed with few layers of reduced graphene oxide (rGO) and obtained by means of a ...facile environment-friendly hydrothermal cosynthesis, is proposed as electrode material for supercapacitors. By electrochemical characterizations in three- and two-electrode configurations and symmetric planar devices, unique results have been obtained, with specific capacitance values up to 416 F g–1 and a highly stable capacitance behavior over 50000 charge–discharge cycles. The in-depth morphological and structural characterizations through field emission scanning electron microscopy, Raman, X-ray photoelectron spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller, and transmission electron microscopy analysis provides the proofs of the unique assembly of such 3D structured matrix. The unpacked MoS2 structure exhibits an excellent distribution of 1T and 2H phase sheets that are highly exposed to interaction with the electrolyte, and so available for surface/near-surface redox reactions, notwithstanding the quite low overall content of MoS2 embedded in the reduced graphene oxide (rGO) matrix. A comparison with other “more conventional” hybrid rGO-MoX2 electrochemically active materials, synthesized in the same conditions, is provided to support the outstanding behavior of the cosynthesized rGO-MoS2.
Dielectric elastomers are smart materials that can be used to conceive solid-state electromechanical transducers such as actuators, sensors, and generators. Dielectric elastomer generators, in ...particular, are very promising for energy harvesting applications because they potentially feature large energy densities, good conversion efficiencies, good shock and corrosion resistance, and low cost. In this article, a novel concept of parallelogram-shaped dielectric elastomer generator is presented and analyzed. Parallelogram-shaped dielectric elastomer generators are rotary variable capacitance transducers, which are made by planar dielectric elastomer membranes that are covered with compliant electrodes and clamped along their perimeter to the links of a parallelogram four-bar mechanism. First, an analytical model for the electro-hyperelastic response of the parallelogram-shaped dielectric elastomer generator is described and used to assess the maximum theoretical performances of the device. Then, an experimental case study with a parallelogram-shaped dielectric elastomer generator prototype featuring a natural rubber dielectric elastomer membrane and carbon conductive grease electrodes is presented. Simulation and experimental results demonstrate the practical feasibility of the parallelogram-shaped dielectric elastomer generator concept.
This paper introduces the novel concept of dielectric fluid transducer (DFT), which is an electrostatic variable capacitance transducer made by compliant electrodes, solid dielectrics and a ...dielectric fluid with variable volume and/or shape. The DFT can be employed in actuator mode and generator mode. In this work, DFTs are studied as electromechanical generators able to convert oscillating mechanical energy into direct current electricity. Beside illustrating the working principle of dielectric fluid generators (DFGs), we introduce different architectural implementations and provide considerations on limitations and best practices for their design. Additionally, the proposed concept is demonstrated in a preliminary experimental test campaign conducted on a first DFG prototype. During experimental tests a maximum energy per cycle of 4.6 mJ and maximum power of 0.575 mW has been converted, with a conversion efficiency up to 30%. These figures correspond to converted energy densities of 63.8 mJ g − 1 with respect to the displaced dielectric fluid and 179.0 mJ g − 1 with respect to the mass of the solid dielectric. This promising performance can be largely improved through the optimization of device topology and dimensions, as well as by the adoption of more performing conductive and dielectric materials.
The sensing capabilities of zinc oxide nano/micro-structures have been widely investigated and these structures are frequently used in the fabrication of cutting-edge sensors. However, to date, ...little attention has been paid to the multi-sensing abilities of this material. In this work, we present an efficient multisensor based on a single zinc oxide microwire/gold junction. The device is able to detect in real time three different stimuli, UV-VIS light, temperature and pH variations. This is thanks to three properties of zinc oxide its photoconductive response, pyroelectricity and surface functionalization with amino-propyl groups, respectively. The three stimuli can be detected either simultaneously or in a sequence/random order. A specific mathematical tool was also developed, together with a design of experiments (DoE), to predict the performances of the sensor. Our micro-device allows reliable and versatile real-time measurements of UV-VIS light, temperature and pH variations. Therefore, it shows great potential for use in the field of sensing for living cell cultures.
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