Photoinduced Autonomous Nonequilibrium Operation of a Molecular Shuttle by Combined Isomerization and Proton Transfer Through a Catalytic Pathway

We describe a [2]rotaxane whose recognition sites for the ring are a dibenzylammonium moiety, endowed with acidic and H-bonding donor properties, and an imidazolium center bearing a photoactive phenylazo substituent. Light irradiation of this compound triggers a network of E/Z isomerization and proton transfer reactions that enable autonomous and reversible ring shuttling away from equilibrium

Artificial supramolecular pumps powered by light

The development of artificial nanoscale motors that can use energy from a source to perform tasks requires systems capable of performing directionally controlled molecular movements and operating away from chemical equilibrium. Here we describe the design, synthesis and properties of pseudorotaxanes in which a photon input triggers the unidirectional motion of a macrocyclic ring with respect to a non-symmetric molecular axle. The photoinduced energy ratcheting at the basis of the pumping mechanism is validated by measuring the relevant thermodynamic and kinetic parameters. Owing to the photochemical behaviour of the azobenzene moiety embedded in the axle, the pump can repeat its operation cycle autonomously under continuous illumination. We use NMR spectroscopy to observe the dissipative non-equilibrium state generated in situ by light irradiation. We also show that fine changes in the axle structure lead to an improvement in the performance of the motor. Such results highlight the modularity and versatility of this minimalist pump design, which provides facile access to dynamic systems that operate under photoinduced non-equilibrium regimes

An Efficient Ray-Based Modeling Approach for Scattering from Reconfigurable Intelligent Surfaces

Reconfigurable Intelligent Surfaces (RISs), which can be implemented using metasurface technology or reflect/ transmit antenna array technology, have garnered significant attention in research studies focused on both their technological aspects and potential applications. While various modeling approaches have been proposed - ranging from electromagnetic simulations and analytical integral formulations to simplified approaches based on scattering matrix theory - there remains a great need for efficient and electromagnetically-consistent macroscopic models that can accurately simulate scattering from RISs, particularly for realistic simulations of RIS-based wireless networks. Building on previous work based on the characterization of the RIS through a surface impedance (or ”spatial modulation”) function and a few parameters, in the present paper we propose a fully ray-based approach for the computation of the re-radiated field that can be easily embedded in efficient, forward ray tracing (also known as ”ray launching”) models. We validate the proposed model by comparison to well established methods available in the literature. Results show that, although the considered method is based on a completely different formulation and is much more efficient than integral formulation methods, results are almost indistinguishable in some benchmark cases

Trace element concentrations in the Mediterranean monk seal (Monachus monachus) in the eastern Mediterranean Sea

The Mediterranean monk seal (Monachus monachus) is one of the most endangered marine mammals in the world. The biggest sub-population of the species survives in Greece, where understanding the effects of pollution on the survival of the species has been identified as a national research and conservation priority. From 1990 to 2013 we collected tissue samples from 59 deceased monk seals in order to: (i) Define the concentration of trace elements (As, Pb, Cd, Hg, Se, Cr, Ni) in three different matrices (i.e., blubber, liver and kidney), (ii) Determine whether differences in trace element concentrations are age- or gender-related, (iii) Evaluate the potential effects of these pollutants. The study recorded differences in trace element concentrations among matrices, but in general, trace element exposure in Mediterranean monk seals in Greece was low and within the non-acutely toxic levels for Pinnipeds. Only arsenic concentrations were at the upper limit of the normal range observed in other marine mammals (0.69 ± 0.55 mg/kg w.w. in blubber, 0.79 ± 0.62 mg/kg w.w. in liver and 0.79 ± 0.59 mg/kg w.w. in kidney). We recorded also exceptionally high Hg concentrations in a single adult female (24.88 mg/kg w.w.). Age- and gender-related differences were also recorded and were due to various biological, ecological and chemical factors. Based on the results of the study, potentially adverse effects on the immune and endocrine system of the Mediterranean monk seal from some pollutants (e.g., As, Cd, Se, Ni, Cr) cannot be ruled out, which may expose the Mediterranean seal population in Greece to epizootics and stochastic phenomena of mass mortality. It is therefore of utmost importance that pollutant monitoring becomes an integral component of the standard monitoring protocol of the endangered Mediterranean monk seal in the eastern Mediterranean